A combined quantum chemical, molcular dynamics and Monto Carlo study of three amino acids as corroison inhibitors for aluminum in NaCl solution

Abstract

The performance of arginine (Arg), glutamine (Glu), and asparagine (Asp) in inhibiting the corrosion of aluminum in NaCl solution and the inhibition mechanism at atomic level are investigated via the combination of the quantum chemistry (QM) calculations, molecular dynamics (MD) and Monte Carlo (MC) simulations to reveal the relationship among chemical structure, composition and performance. QM results show that differences in EHOMO, ELUMO, ΔEgap, dipole moment, global softness and hardness, and ESP charge lead to differences in inhibition efficiency. MC results show that the adsorption energy in aqueous environment for Arg, Glu, and Asp is −210.39, −69.22, and −66.88 Kcal mol−1, respectively. Results showed that inhibition efficiency is high when the absolute value of adsorption energy is high. MD simulation show that the peak distance of relative concentration function of Cl- is 17.45, 18.96, and 20.06 Å for Arg, Glu and Asp, respectively. The diffusion coefficient of Cl- in inhibitor film for Arg, Glu, Asp is 5.18 × 10−8, 8.01 × 10−8, 1.22 × 10−7 cm2 s−1, respectively. Both the adsorption energy and the ability to inhibit the diffusion and aggregation of corrosion particles determine the corrosion inhibition performance. The theoretical calculated inhibition ability is Arg＞Glu＞Asp, in good agreement with the experiment results. This paper provides a theoretical reference for further research on amino acid corrosion inhibitors.